JP2000238325A - Organic el print head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectuate high image-quality exposure by emitting R, G and B lights from an equal point of light emission dots. SOLUTION: An organic EL element 23A for projecting a red light, an organic EL element 23B for projecting a blue light and an organic EL element 23C for projecting a green light are sequentially perpendicularly layered on a substrate 21. Light emission dots of the organic EL elements 23A, 23B and 23C are arranged in a serpentine form in a main scanning direction. Each of the organic EL elements 23A, 23B and 23C has an organic layer including a light emission layer 27 layered between an anode 24 and a cathode 28. Among light emission layers 27A, 27B and 27C, a light emission area of the layer of a lowest exposure efficiency is largest and is smaller as the exposure efficiency is higher. The layers are formed with center points registered.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescence (hereinafter referred to as "organic electroluminescence") having a plurality of light emitting dots.
Organic EL that forms a color image using an element)
Regarding the print head.

[0002]

2. Description of the Related Art An organic EL device has a structure in which a thin organic layer containing a fluorescent organic compound is sandwiched between a cathode serving as an electron injection electrode and an anode serving as a hole injection electrode. A display element that generates excitons (excitons) by injecting and recombining holes and injects light to emit light (fluorescence / phosphorescence) when the excitons are deactivated.

In recent years, there has been proposed an optical printer using the organic EL element as a light source. 6 is a configuration diagram of an organic EL array print head disclosed in Japanese Patent Application Laid-Open No. 9-226172, FIG. 7 is a plan view of the head, and FIG. 8 is a cross-sectional view taken along line AA of FIG.

[0006] In this organic EL array print head, as shown in FIG. 6, an organic EL array substrate 53 having an organic EL array 52 and a plurality of driver ICs 54 are arranged on a chip-on-board substrate 51. The bonding wires 55 electrically connect between the chip-on-board substrate 51 and the driver IC 54, between the driver IC 54 and the organic EL array substrate 53, and between the chip-on-board substrate 51 and the organic EL array substrate 52, respectively. ing. Then, the light emitted from the organic EL array 52 is emitted to the back side of the glass substrate, and is condensed on the photosensitive drum 57 via the converging rod lens array 56.

The structure of the organic EL array substrate 53 will be further described. As shown in FIGS. 7 and 8, a transparent electrode 62 having a predetermined pattern is formed on a glass substrate 61. An insulating film 65 is formed in a region other than the first contact hole 63 and the second contact hole 64. A hole transport layer 66 and a light emitting layer 67 are formed to include the second contact hole 64 of the insulating film 65, and an electron injection electrode 68 is formed to include the hole transport layer 66 and the light emitting layer 67. I have. On the electron injection electrode 68, a protective film 71 is formed in a region other than the first contact hole 69 and the second contact hole 70. On the protective film 71, a signal electrode 72 having a predetermined pattern is formed. Further, the first contact hole 6 of the protection film 71 is formed.
9, a common electrode 73 having a predetermined pattern is formed.

In the organic EL array print head configured as described above, data of contents to be printed is sent to the driver IC 54 on the chip-on-board substrate 51. The dots whose data sent to the driver IC 54 are “ON” are provided with the bonding wires 5 from the driver IC 54.
A current is supplied to the signal electrode 72 via the terminal 5. No current is supplied to the signal electrode 72 from the driver IC 54 via the bonding wire 55 to the dot whose data is “OFF”.

The current from the signal electrode 72 passes through the first contact hole 63 of the insulating film 65, flows into the transparent electrode 62, and causes holes to be injected into the hole transport layer 66. Electrons are injected from the electron injection electrode 68 into the light emitting layer 67. As a result, the electrons move in the light emitting layer 67 toward the hole transport layer 66, and when they reach the interface with the hole transport layer 66, the movement is blocked by a difference in electron affinity.

On the other hand, holes move in the hole transport layer 66 toward the light emitting layer 67, and when they reach the interface with the light emitting layer 67, they are easily injected into the light emitting layer 67. Is done. The injected holes recombine with the electrons waiting in the light emitting layer 67, and the recombination energy causes the light emitting layer 67 to be excited. Then, when returning to the ground state, it emits fluorescence, and this light emission is emitted to the outside toward the back side of the glass substrate 61. Thereafter, the emitted light is condensed on the photosensitive drum 57 via the converging rod lens array 56 and is irradiated for a required time to form a desired latent image on the recording paper.

[0009]

When the conventional organic EL array print head configured as described above is used as a light source of a self-coloring type color printer, the organic fluorescent material is used for each of R, G, and B colors. It is conceivable that the light emitting layer 67 is formed by applying different colors to form light emitting dots that emit light of each color of R, G, and B.

However, in the case of the above configuration, the R, G, and B light emitting dots are arranged at different places,
Three rows of Selfoc lens arrays are required to form the R, G, and B lights of each color as an erect equal-magnification image on the surface of the recording medium, and misalignment of each array is likely to occur during assembly. Problems arise. Moreover, the MTF (Modulation Transcript) indicating the optical performance of the SELFOC lens array
There is a problem that it cannot be used where the sfer function is large.

Here, the MTF indicates the quality of an image, that is, the resolution, which is important in evaluating the image transmission characteristics of the Selfoc lens array. The MTF, which is a response function of the selfoc lens array, is obtained by scanning an image of a rectangular wave grating pattern or receiving an image by a CCD image sensor, and calculating the following equation (1) from the light amount level.
It is calculated from:

MTF (w) = [i (w) max−i (w) min / i (w) max + i (w) min] × 100 (%) Equation (1)

Note that i (w) max and i (w) min are spatial frequencies w
The maximum and minimum values of the square wave response at (lp / mm).
The closer the MTF is to 100%, the more an image faithful to the original image is formed.

Further, if the light emitting dots of each color of R, G, B are arranged at different places, the light emitting dots of each color will be delayed in exposure, causing high quality image exposure due to the cause of image unevenness. Can not.

In view of the above, the present invention has been made in view of the above problems, and provides an organic EL print head capable of emitting light of different emission spectrum distribution from the same spot of a light emitting dot and capable of performing exposure with high image quality. It is intended to be.

[0016]

In order to achieve the above object, the invention according to claim 1 is characterized in that an organic layer including a light emitting layer is provided between a first electrode and a second electrode, at least one of which has translucency. An organic EL print head, which is formed by laminating on a substrate and selectively irradiates dot-shaped light obtained by light emission of the light-emitting layer to a recording medium via an electrode having a light-transmitting property to form an image. A plurality of organic EL elements each having a different emission spectrum distribution in which an organic layer including a light-emitting layer is stacked between one electrode and the second electrode are vertically stacked on the substrate; The light emitting dots of the organic EL element are arranged in a line or in a staggered manner in the main scanning direction.

According to a second aspect of the present invention, in the organic EL print head according to the first aspect, each of the light emitting layers of the plurality of organic EL elements is formed with substantially the same light emitting area, and the amount of light irradiated on the recording medium is recorded. Light emission is driven by varying input power so as to obtain an optimum color balance in accordance with the sensitivity of the medium.

According to a third aspect of the present invention, in the organic EL print head of the first aspect, each light emitting layer of the plurality of organic EL elements is driven to emit light by inputting the same power, and the amount of light applied to the recording medium is recorded. According to the sensitivity of the medium, the respective light emitting layers are stacked from the substrate side in order from the light emitting layer having a lower exposure ability so as to have an optimal color balance, and the light emitting area is formed smaller as the light emitting layer has a higher exposure ability. It is characterized by being.

According to a fourth aspect of the present invention, in the organic EL print head according to any one of the first to third aspects, the light-emitting dots are formed by interpolating a gap in the main scanning direction and forming an area of one line in the main scanning direction on the recording medium. The light emitting dots are arranged such that the width of the light emitting dots in the main scanning direction and / or the width of the sub scanning direction is changed so that the amount of light irradiated on the recording medium is adjusted to the sensitivity of the recording medium, and the optimum color is obtained. It is characterized in that it is formed with a light-emitting area according to a balanced luminance ratio.

According to a fifth aspect of the present invention, in the organic EL print head of the fourth aspect, the width of the luminescent dots is the same between centers in the sub-scanning direction, and the recording is performed by changing at least the width in the sub-scanning direction. It is characterized in that the light amount applied to the medium is adjusted to the sensitivity of the recording medium, and is formed with a light emitting area corresponding to a luminance ratio that provides an optimal color balance.

According to a sixth aspect of the present invention, in the organic EL print head according to any one of the first to fifth aspects, the organic EL elements are so arranged that the images of the respective colors overlap at the same position on the recording medium in accordance with the image signals of the respective colors. A color image is formed on the recording medium by controlling and performing multiple exposure.

[0022]

FIG. 1 is a schematic diagram of an organic EL printer (optical printer) having an organic EL print head according to the present invention. FIG. 2 is a diagram showing an embodiment of the organic EL print head. FIG. 3 is a schematic plan view showing an outline of the electrode structure viewed from the outside of FIG. 3, and FIG. 3 is a partially enlarged cross-sectional view of the organic EL print head, taken along line AA in FIG. 2 and observed from the main scanning direction. It is an expanded sectional view. Note that FIG.
Omits the sealing cap.

First, before describing the structure of the organic EL print head 2, a schematic configuration of the organic EL printer 1 will be described with reference to FIG.

The organic EL printer 1 includes an organic EL print head 2 as a light source. The light of the three primary colors R, G, and B obtained from the organic EL print head 2 is applied to a recording medium W such as a color film. Writing is performed by one scan to form a full-color image.

The organic EL printer 1 is driven by a digital color image signal obtained from a video device or the like, and is used as a color video printer for printing an image on a recording medium W in full color. In addition, it can be used for an electrophotographic printer, a silver halide printer, a label printer, and the like.

As shown in FIG. 1, the organic EL printer 1
With respect to the recording medium W positioned and fixed at a predetermined location,
In addition to the organic EL print head 2 moving along the sub-scanning direction indicated by the arrow A, light from the light emitting unit 3 of the organic EL print head 2 is formed on the surface of the recording medium W as an erect equal-magnification image. A single optical system 6 including a selfoc lens array 4 and a reflecting mirror 5 as light collecting means is built in the housing 12.

Although not shown, the SELFOC lens array 4 as a light condensing means has SELFOC lenses regularly and precisely arranged between two frame plates corresponding to respective light emitting dots of the organic EL print head 2 described later. It was done. The gap between the selfoc lens arrays 4 is filled with a black silicone resin in order to remove flare light. For the two frame plates, a material having substantially the same characteristics as the thermal expansion of the SELFOC lens (for example, a glass cloth base epoxy resin black laminate) is used. As a result, thermal strain on the SELFOC lens is reduced, and the strength of the SELFOC lens array is increased.

As shown in FIG. 1, the housing 12 containing the organic EL print head 2 reciprocates in the sub-scanning direction with respect to the recording medium W by the moving mechanism 7 as moving means. The moving mechanism 7 includes a guide unit (not shown) that guides the housing 12 containing the organic EL print head 2 so as to be movable in the sub-scanning direction, a pair of pulleys 9 around which a drive belt 8 is wound, and a pulley 9. , 9 for rotating one of them.

The housing 12, which incorporates the organic EL print head 2 and is fixed to the drive belt 8, is driven by a drive motor 10 to circulate the drive belt 8, and is guided by guide means (not shown) to It can move along the scanning direction. A plurality of color films as the recording medium W are held at predetermined positions, and when writing by light is completed, the discharge mechanism 11 performs development and discharges the color film to the outside of the housing 12 at the same time.

Next, the structure of the organic EL print head 2 will be described with reference to FIGS. In FIG. 2, a pattern adopting the pattern of FIG. 5A described later is shown as the light emitting pattern of the light emitting dot.

The organic EL print head 2 is based on a transparent and insulating substrate 21 made of glass or the like. On the substrate 21, two sets of light emitting pattern groups 22A having different emission spectrum distributions at substantially the same location are provided. , 22B
Are formed in a staggered manner in the sub-scanning direction.

Each of the light emitting pattern groups 22A and 22B is composed of three sets of organic EL layers vertically stacked on the substrate 21.
The light emitting portion (light emitting dot) 3 is formed by the element 23 (23A, 23B, 23C). These three sets of organic EL elements 23 can be individually controlled in light emitting dot units by statically driving each light emitting dot, and light of a predetermined color (red, blue, green, or (Mixed color).

Three sets of organic EL elements 23A, 23B, 23
C is a light emission drive and a color balance
It is formed by vertically stacking on the substrate 21 in the order of insufficient light emission intensity (light quantity). In the examples of FIGS. 2 and 3, red, blue, and green are arranged in the order in which the light emission intensity indicating the exposure capability is insufficient. First, an organic EL element 23 </ b> A that emits red light is formed on the substrate 21.

In forming the organic EL element 23A, the anode 24A as a transparent first electrode is formed on the substrate 21.
(24) is formed. The material of the anode 24A is ITO (composite oxide of indium oxide and tin) or IDIXO (trade name: Idemitsu Indium X-Metal Oxid
e, a complex oxide having a surface work function of 4.0 ev or more, such as a composite oxide of indium oxide and zinc oxide). In the example shown in FIG. 2, the anodes 24A are arranged in two rows in a staggered manner in the sub-scanning direction, and are provided for each light emitting dot. Above the anode 24A, a light-emitting layer 27A (27) that emits a red dot light is formed in a later step.

The insulating layer 25 is formed on the anode 24A so that red light emitting dots are arranged in a staggered manner in the sub-scanning direction at a predetermined interval. As shown in FIG. 3, an opening 25a having a size and shape corresponding to the pattern shape of the light emitting dots of the light emitting layer 27A described later is provided in a portion corresponding to the anode 24A in the insulating layer 25 to expose the anode 24A. .
The opening 25a functions as a frame that partitions the light emitting dots of the light emitting layer 27A. The insulating layer 25 is formed on the entire surface of the substrate 21 by spin coating, vapor deposition, sputtering, or the like using photosensitive polyimide, SiO ₂ , SiN, or the like as a material. Then, a part of the insulating layer 25 is patterned by using a photolithography method to form openings 25a having a staggered pattern substantially similar to that of the anode 24A.

An organic layer 26 of a hole injection layer or a hole transport layer is formed from above the opening 25a to be a light emitting area by a resistance heating evaporation method so as to fill the opening 25a. The film is formed by bringing a metal mask corresponding to the light emitting area (opening 25a) into close contact with the substrate 21.

At this time, the hole injection layer and the hole transport layer are preferably made of a material transparent to the visible region. As a material for forming the hole injection layer, m represented by the chemical formula (Formula 1) is used.
−MTDATA, that is, 4,4 ', 4''-tris (3-methylphenylphenylam
There is ino) triphenylamine. As a material for forming the hole transport layer, TPD represented by chemical formula (Formula 2), that is,
N, N'-diphenyl-N, N'-bis (3-methylphenyl) -1,1'-biphen
yl-4,4'-diamine and α-NP shown in chemical formula (3)
D, that is, N, N'-bis- (1-naphthyl) -N, N'-diphenylbenzidine;

[0038]

Embedded image

[0039]

Embedded image

[0040]

Embedded image

A light emitting layer 27 as an organic layer emitting red light is provided in a portion corresponding to the opening 25a serving as a light emitting area.
A (27) is formed. The light emitting layer 27A corresponding to the red light emitting dots is formed through a metal mask in a region that sufficiently covers the light emitting area. The selection of the light emitting material for forming the light emitting layer 27A is determined by the light emission spectrum, the light emission efficiency of the organic fluorescent material to be used, and the photosensitive sensitivity characteristics of the recording medium W, and the light emission intensity is best when the color balance is achieved. (Light quantity) is formed of an organic phosphor having a shortage.

On the organic layer 26 laminated on the light emitting layer 27A, a cathode 28A (28) is formed as a second electrode. The cathode 28A is formed of a material having a small work function so that electrons can be easily injected at the interface with the light emitting layer 27A (or the electron transport layer). As a material that can obtain good characteristics, a simple substance such as Li, Na, Mg, and Ca, a compound thereof, or various alloys such as Al: Li, Mg: In, and Mg: Ag can be used. The cathode 28A is formed of a thin film of 50 nm or less in order to improve the transmittance.

In the portion where the cathode 28A and the anode 24A intersect, for example, a rectangular shape shown in FIG. 2 or FIG.
There is a light emitting region composed of any one of the patterns (a) to (d).

Organic EL emitting red light on substrate 21
When the element 23A is formed, an organic EL element 23B that emits blue light is formed thereon.

In forming the organic EL element 23B, the anode 24B as the transparent first electrode is formed by the same material and the same method as the anode 24A of the organic EL element 23A.
(24) is formed on the cathode 28A of the organic EL element 23A. Above the anode 24B, a light emitting layer 27B (27) that emits light in a blue dot shape is formed in a later step.

On the anode 24B, an organic layer 26 of a hole injection layer or a hole transport layer is formed by using a resistance heating evaporation method. The film is formed by bringing a metal mask corresponding to the light emitting area into close contact with the substrate 21. Further, on the organic layer 26, a light emitting layer 27B (2
7) is formed. The light emitting layer 27B corresponding to the blue light emitting dots is formed through a metal mask in a region that sufficiently covers the light emitting area. The selection of the light emitting material for forming the light emitting layer 27B is determined by the light emission spectrum, the light emission efficiency, and the sensitivity characteristic of the recording medium W of the organic fluorescent material to be used. ) Is formed of the second deficient organic phosphor.

On the organic layer 26 laminated on the light emitting layer 27B, a cathode 28B (28) as a second electrode is formed. The cathode 28B is provided so that electrons can be easily injected at the interface with the light emitting layer 27B (or the electron transporting layer).
Like A, it is formed of a material having a small work function. Cathode 28
B is formed as a thin film having a thickness of 50 nm or less in order to improve the transmittance.

At the portion where the cathode 28B and the anode 24B intersect, for example, a rectangular shape shown in FIG. 2 or FIG.
There is a light emitting region composed of any one of the patterns (a) to (d). The blue light-emitting region has the same width in the main scanning direction and the width in the sub-scanning direction as the red light-emitting region in the examples shown in FIGS. 2 and 3 and is smaller than the red light-emitting region as a whole. The area is small.

When an organic EL element 23B that emits blue light is formed vertically on an organic EL element 23A that emits red light, an organic EL element 23C that emits green light is formed thereon.
Are formed vertically.

In forming the organic EL element 23C, the anode 24C as the transparent first electrode is formed by the same material and the same method as the anode 24A of the organic EL element 23A.
(24) is formed on the cathode 28B of the organic EL element 23B. Above the anode 24C, a light emitting layer 27C (27) that emits light in a green dot shape is formed in a later step.

On the anode 24C, an organic layer 26 of a hole injection layer or a hole transport layer is formed by using a resistance heating evaporation method. The film is formed by bringing a metal mask corresponding to the light emitting area into close contact with the substrate 21. Further, on this organic layer 26, a light emitting layer 27C (2
7) is formed. The light emitting layer 27C corresponding to the green light emitting dots is formed via a metal mask in a region that sufficiently covers the light emitting area. The selection of the light emitting material for forming the light emitting layer 27C is determined by the light emission spectrum, the light emission efficiency of the organic fluorescent material to be used, and the sensitivity characteristic of the recording medium W. ) Is formed of the highest organic phosphor.

On the organic layer 26 laminated on the light emitting layer 27C, a cathode 28C (28) is formed as a second electrode. The cathode 28C is provided so that electrons can be easily injected at the interface with the light emitting layer 27C (or the electron transport layer).
Like A, it is formed of a material having a small work function.

In the portion where the cathode 28C and the anode 24C intersect, for example, a rectangular shape shown in FIG. 2 or FIG.
There is a light emitting region composed of any one of the patterns (a) to (d). The green light-emitting region has the same width in the main scanning direction and the width in the sub-scanning direction as the red and blue light-emitting regions in the examples shown in FIGS. The area is smaller than the light emitting region. .

Here, the light emitting portions 3 (light emitting layers 27) of the light emitting pattern groups 22A and 22B are staggered so as to cover the area of one line in the main scanning direction of the recording medium W by interpolating the gap in the main scanning direction. It is arranged in a shape. More specifically, the light emitting pattern groups 22A and 22B emit light so as to interpolate between the adjacent light emitting layers 27 of the light emitting pattern group 22A in the main scanning direction when the side surface of the substrate 21 is viewed from the sub-scanning direction. The light emitting layer 27 of the pattern group 22B is formed. That is, in FIG. 2, the width in the main scanning direction of the light emitting layer 27 in the upper row of light emitting pattern groups 22A is such that the end in the sub scanning direction is equal to the end in the sub scanning direction of the light emitting layer 27 in the lower row of light emitting pattern groups 22B. Dimensions are uniform or overlap.

The anode 24 may be arranged so that the light emitting dots of the light emitting layer 27 are arranged in a line at a predetermined interval. However, in such a case, a space for electrically separating the anode is required. In addition, the light emitting dots must be substantially reduced, and when the recording medium W is exposed, uneven streaks occur. Further, in order to draw out each anode 24 in a direction orthogonal to the direction in which the luminescent dots are arranged, the width must be narrower than the state shown in FIG. This is not a preferable structure for the anode 24 formed of ITO having high resistivity. If the light emitting dots are arranged in a staggered manner as in this example, the anodes 24 can be easily arranged and the thickness can be doubled as compared with the case of one row, so that the resistance can be suppressed to a preferable low.

The light emitting layers 27A of the R, G, and B colors described above,
27B and 27C are formed by using a material whose center wavelength of the emission spectrum matches the sensitivity of the photosensitive material so that a full-color image can be formed by the photosensitive material of the recording medium W.

FIG. 4 shows an example of the sensitivity characteristic of the photosensitive material of the recording medium W (color film). Tables (Tables 1 to 3) show examples of the organic phosphor material (light emitting layer 23) which can correspond to the emulsion having the sensitivity characteristics shown in FIG. Table 1 shows red light emitting materials, Table 2 shows blue light emitting materials, and Table 3 shows green light emitting materials.

[0058]

[Table 1]

[0059]

[Table 2]

[0060]

[Table 3]

Each of the organic phosphors has optimum film forming conditions according to the material. Each of them may be used as a single layer film or may be used after being doped into an appropriate host material.

After forming the light emitting layers 27A, 27B, and 27C for each color, an electron transporting layer, which is an organic layer, is formed on the light emitting layers as necessary. This is also determined according to the characteristics of the organic phosphor material used. .

On the substrate 21, the organic EL elements 23A, 23
After the formation of 3B and 23C, the sealing cap 31 as a sealing member is sealed on the upper surface of the substrate 21 in an inert gas from which moisture has been sufficiently removed, and sealing is performed. Complete the process.

Here, FIGS. 5A to 5D show R, G,
When obtaining the color balance of each of the B colors, the organic EL element 23A,
A pattern example of light emitting dots applicable to the light emitting layers 27A, 27B, and 27C of 23B and 23C is shown. FIGS. 5A to 5D show the respective patterns of R, G, and B separately.

First, in the light emitting dot patterns shown in FIGS. 5A to 5C, the width in the main scanning direction is equal, and the width in the sub scanning direction is changed to give a gradation. This allows R,
The light emitting layers 27A, 27A,
The light emission areas of 27B and 27C are corrected.

In the light emitting dot pattern shown in FIG.
Within the reference area of each light emitting dot (corresponding to a dot area of width a × a), gradation is given by changing the width in the main scanning direction and the sub-scanning direction. As a result, the light emitting layers 27A, 27B,
The light emission area of 27C is corrected.

The light emitting layer 27 (27A, 27B, 2)
The pattern of the light emitting dots of 7C) is divided so that the area integration amount in the sub-scanning direction is the same at each position in the main scanning direction.

In FIG. 5A, each light emitting layer 27A, 2
7B and 27C are composed of one pattern. Each of the light-emitting layers 27A, 27B, and 27C has the same width a in the main scanning direction, and is formed by stacking so that the center points coincide. Also,
The width c (c1, c2, c3) in the sub-scanning direction of each pattern of the light emitting layers 27A, 27B, 27C has different dimensions.

In the example shown, the light emitting layers 27A, 27B, 2
The width c (c1, c2, c3) in the sub-scanning direction is set so that the area ratio of 7C is 1: 2: 3. The ratio of the widths c1, c2, and c3 in the sub-scanning direction is determined by the sensitivity characteristics of the recording medium W used, the emission spectrum of the material used for the light emitting layer 27, and the light emission efficiency in order to obtain an optimal color balance. You.

The specific numerical values are shown as follows.
The patterns 7B and 27C have a width a in the main scanning direction of 0.1.
2 mm. The light emitting layer 23A that emits red light has a width c2 in the sub-scanning direction of the pattern of 0.12 mm. The light emitting layer 23B that emits blue light has a width c in the sub-scanning direction of the pattern.
3 is 0.08 mm. Light-emitting layer 27C that emits green light
Has a width c1 in the sub-scanning direction of the pattern of 0.04 mm.

In FIG. 5B, each light emitting layer 27A, 2
7B and 27C have the same width a in the main scanning direction,
The laminations are formed so that the center points coincide. Further, within the reference area (corresponding to the dot area of width a × a), the light emitting layer 27
A width c in the sub-scanning direction of each pattern of A, 27B and 27C
(C1, c2, c3) have different dimensions.

In the illustrated example, the light emitting layer 27A is constituted by one pattern, and the light emitting layer 27B and the light emitting layer 27C are constituted by two patterns. Then, the light emitting layers 27A, 27B, 27
The width c (c1, c2, c3) of each pattern in the sub-scanning direction is set such that the area ratio of C is 1: 2: 3. The ratio of the widths c1, c2, and c3 in the sub-scanning direction is determined by the sensitivity characteristics of the recording medium W used, the emission spectrum of the material used for the light emitting layer 23, and the light emission efficiency in order to obtain an optimal color balance. You.

The specific numerical values are as follows.
The patterns 7B and 27C have a width a in the main scanning direction of 0.1.
2 mm. The light emitting layer 27A has a width c2 in the sub-scanning direction of 0.12 mm (= a). The width of the upper and lower ends of the two patterns in the sub-scanning direction of the light emitting layer 27B is 0.12 mm (=
a), wherein the width c3 of one pattern in the sub-scanning direction is 0.04 mm. In the light emitting layer 27C, the width of the upper and lower ends of the two patterns in the sub-scanning direction is 0.12 mm (= a), and the width c1 of one pattern in the sub-scanning direction is 0.02 mm.
mm.

The pattern shown in FIG. 5C is a modified example of FIG. 5B, and relates to the light emitting layers 27B and 27C for correcting the light emitting area within the reference area (corresponding to the dot area of width a × a). The light emitting layers 27B and 27C are further divided into a plurality of patterns in the sub-scanning direction.

In the illustrated example, the light emitting layer 27A is constituted by one pattern, and the light emitting layer 27B and the light emitting layer 27C are constituted by four patterns. Then, the light emitting layers 27A, 27B, 27
The width c (c1, c2, c3) of each pattern in the sub-scanning direction is set such that the area ratio of C is 1: 2: 3. The ratio of the widths c1, c2, and c3 in the sub-scanning direction is determined by the sensitivity characteristics of the recording medium W used, the emission spectrum of the material used for the light emitting layer 23, and the light emission efficiency in order to obtain an optimal color balance. You.

The specific numerical values are as follows.
The patterns 7B and 27C have a width a in the main scanning direction of 0.1.
2 mm. The light emitting layer 27A has a width c2 in the sub-scanning direction of 0.12 mm (= a). In the light emitting layer 27B, the width of the upper and lower ends of the two patterns located at the upper and lower ends in the sub-scanning direction is 0.12 mm (= a), and the width c3 of one pattern in the sub-scanning direction is 0.02 mm. . Light emitting layer 27C
The width of the upper and lower ends of the two patterns located at the upper and lower ends in the sub-scanning direction is 0.12 mm (= a), and the width c1 of one pattern in the sub-scanning direction is 0.01 mm.

In FIG. 5D, each light emitting layer 27A, 2
Reference numerals 7B and 27C denote a width c in the main scanning direction a (a1, a2, a3) and a width c in the sub-scanning direction of each pattern of the light emitting layers 27A, 27B, 27C within a reference area (corresponding to a dot area of width a × a). (C1, c2, c3) have different dimensions.

In the illustrated example, the light emitting layer 27A is constituted by one pattern, and the light emitting layer 27B and the light emitting layer 27C are constituted by 14 patterns. Then, the light emitting layers 27A, 27B, 2
The width a (a1, a2, a3) in the main scanning direction and the width c (c1, c2, c3) in the main scanning direction of each pattern are set so that the area ratio of 7C is 1: 2: 3. . The widths a1, a2, a3 in the main scanning direction and the widths c1, c in the sub-scanning direction
The ratio of 2 and c3 is determined by the sensitivity characteristics of the recording medium W used, the emission spectrum of the material used for the light emitting layer 23, and the light emission efficiency in order to obtain an optimal color balance.

Specifically, the light emitting layer 27A has a width a2 in the main scanning direction and a width c2 in the sub scanning direction of 0.
12 mm. The light emitting layer 27B is located at the left and right ends.
The width of the left and right edges in the main scanning direction of the two patterns and the width of the upper and lower edges in the sub scanning direction of the two patterns located at the upper and lower edges are 0.1
The width a3 in the main scanning direction and the width c3 in the sub-scanning direction of one pattern are 0.0227 mm. The width of the left and right ends of the two patterns located at the left and right ends in the main scanning direction and the upper and lower ends of the two patterns located at the upper and lower ends in the sub scanning direction are 0.12 mm (=
a), the width a1 in the main scanning direction and the width c1 in the sub-scanning direction of one pattern are 0.0185 mm.

The specific numerical values in the light emitting patterns shown in FIGS. 5A to 5D are the light emitting layers 27 (27A, 27B, 2).
7C) using an appropriate color organic fluorescent material as
This is an example of a case where area correction corresponding to a luminance ratio of G: B: R = 1: 2: 3 is performed.

The pattern of the light emitting dots of the light emitting layer 27 has a width in the main scanning direction, which is the moving direction of the organic EL print head 2, so that the streak or the like does not easily appear when the recording medium W is exposed. It is preferable to provide a non-light-emitting portion parallel to the main scanning direction without any change. This is organic E
Because the recording medium W is sequentially exposed by moving the L print head 2 in the sub-scanning direction, line defects in the main scanning direction are hardly affected by the image quality.

Therefore, the pattern of the light emitting dots of the light emitting layer 27 is not limited to those shown in FIGS. 5A to 5D as long as the pattern shape satisfies the above conditions. The width H between the patterns of the light emitting layer 27 in the sub-scanning direction is set to be equal to or larger than the width a of the reference region in the sub-scanning direction.

By the way, the organic EL print head 2
In the configuration of R, R of each light emitting pattern group 22A, 22B,
The light emitting dots of each color G and B are corrected to have an area corresponding to the luminance ratio so that the light amount of all the light emitting dots is constant. However, the light emitting dots of each of the light emitting dots R, G and B of each light emitting pattern group 22A and 22B are corrected. The area may be the same area, and the power (drive current density) or pulse width applied to the light emitting dots (light emitting layers 27A, 27B, 27C) of each color may be varied in accordance with the luminance ratio.

When driving the organic EL print head 2 configured as described above, each light emitting dot is driven statically. At this time, the uppermost cathode 28C is at the ground level, and the other cathodes 28C are not grounded.
A and 28B also act as anodes of other colors. A driver for control is connected to the electrode of each color, and image data (image signal) stored in the image memory, respectively.
, And the organic E is turned on in synchronization with the timing so that the R, G, and B images overlap the same position on the recording medium W.
The L print head 2 is moved in the sub-scanning direction. By one moving scan of the organic EL print head 2, the same spot on the recording medium W can be subjected to multiple exposures of dot light of each color of R, G, and B as needed.

According to the organic EL print head 2 of the above embodiment, the following features (1) to (6), which are useful when compared with a print head using a fluorescent display tube, are utilized. The following effects are obtained.

(1) Power consumption is reduced to 1/3 to 1/5 as compared with a print head using a fluorescent display tube. (2) The material thickness of the substrate is 1.1 regardless of the size of the device.
mm or less, and the thickness as a device is 1/3 to 1 /
It becomes 5. (3) The weight is reduced to half or less. (4) The dead space is small and downsizing is possible. (5) Fluctuations in light emission characteristics are small and correction is easy. (6) In the external color filter switching method, it is necessary to move the head three times to write one full-color screen, whereas full-color reproduction can be performed by one process exposure.

The organic EL print head 2 of the present embodiment
Is provided with two sets of light emitting pattern groups 22A and 22B having a plurality of light emitting dots arranged in a staggered manner in the sub-scanning direction, and the light emitting dots of each light emitting pattern group 22A and 22B are R, G, and
The light emitting layers 27A, 27B, and 27C of B are vertically stacked on the substrate 21 with a pair of electrodes (anode 24 and cathode 28) interposed therebetween, so that the light emitting dots of each color can be individually controlled. ing. Accordingly, a full-color image of good image quality can be formed on the recording medium W by moving the organic EL print head 2 only once in the sub-scanning direction.

The luminous intensity of the luminous dots of each color is corrected by the luminous area, applied voltage, pulse width, etc. in order to achieve color balance. Therefore, the exposure of a full-color image under the optimum conditions suitable for the photosensitive sensitivity characteristics of the recording medium W It can be performed.

The light emitting dots of the light emitting pattern groups 22A and 22B are formed by laminating the R, G, and B light emitting layers 27A, 27B, and 27C at substantially the same position with their centers aligned. Is focused on the surface of the recording medium W as an erect equal-magnification image, the SELFOC lens array 4 can be used in a place where the MTF is optimal. In addition, since the SELFOC lens array 4 can be commonly used for the R, G, and B light emitting dots, it is more resistant to misalignment at the time of assembling than a conventional configuration that requires a SELFOC lens array for each color. Light amount unevenness can be reduced.

R, G, and R of the light emission pattern groups 22A and 22B
Since the light emitting dots of each of the B colors are formed by lamination in substantially the same place, the drive control of each light emitting dot becomes easy, the delay of the exposure is reduced, and the recording medium W can be exposed with high image quality.

Each light-emitting pattern group 22 depends on the sensitivity characteristics of the recording medium W used and the light-emitting spectrum of the light-emitting layer 27.
If the correction is performed by giving the light emitting dots of the light emitting layer 27 in A and 22B an area gradation, the power per unit area (drive current density) applied to the light emitting layer 27 of each of the light emitting pattern groups 22A and 22B can be reduced. The light quantity can be corrected so that the light emission luminance of all the light emitting layers 27 is maintained at an optimum color balance without being varied.

In addition, each light emitting pattern group 22A, 22B
Since the power per unit area applied to the light emitting layer 27 is constant, the operating voltage can be shared, and the deterioration speed of each light emitting layer 27 can be made uniform. As a result, the color balance does not change, so that a high-quality image with excellent color reproducibility can be stably obtained.

Specifically, when the light emitting pattern shown in FIG. 5A is used for the light emitting dots of the light emitting layer 27, the light emitting portions 3 (light emitting layer 27) of the light emitting pattern groups 22A and 22B are arranged in the main scanning direction of each color. Are the same, the effect of line defects in the main scanning direction is small, and an image with less streaks can be obtained.

Further, when any of the light emitting patterns shown in FIGS. 5B to 5D is employed for the light emitting layer 27, the light emitting portions 3 (light emitting layer 27) of the light emitting pattern groups 22A and 22B are arranged in the sub-scanning direction. Since the dot size does not change, the size of each color in the main scanning direction is the same, and the width in the sub-scanning direction is divided within the reference area, line defects in the main scanning direction and the sub-scanning direction are not sacrificed without sacrificing resolution. , And a high-quality image with less influence of uneven streaks can be obtained.

In the above-described embodiment, the organic EL is used for the recording medium W positioned and fixed at a predetermined position.
Although the print head 2 is reciprocated in the sub-scanning direction to perform desired surface exposure on the recording medium W, the organic EL print head 2 is positioned and fixed at a predetermined position, and the organic EL print head 2 thus positioned and fixed is fixed. However, the recording medium W may be moved in the sub-scanning direction. That is, the organic EL print head 2 and the recording medium W may be configured to be relatively movable in the sub-scanning direction.

Further, as the organic EL print head 2,
Although the configuration in which the light-emitting dots are arranged in a staggered manner has been described, if the light-emitting dots are arranged so as to cover an area of one line in the main scanning direction of the recording medium W, the light-emitting dots of the same color are arranged in one line in the main scanning direction. They may be arranged side by side, or two or more rows of light emitting dots may be formed in parallel with the main scanning direction.

Further, the organic EL elements 23A, 23B, 23
C indicates that the first electrode is connected to the anode 24 (24A, 24B, 24A).
C) and the second electrode is a cathode 28 (28A, 28B, 2).
Although described as 8C), a configuration in which the anode 22 and the cathode 28 are reversed may be adopted. In this case, the laminated structure of the organic layers is also reversed.

In the organic EL print head 2 of the above embodiment, as the light emitting layers 27 having different emission spectrum distributions, a light emitting layer 27A that emits red light, a light emitting layer 27B that emits blue light, and a light emitting layer 27C that emits green light. Although the configuration has been described as including the organic EL device in which two or more light emitting layers having different emission spectrum distributions are stacked,
Any configuration that is vertically stacked on top may be used.

[0099]

As is apparent from the above description, according to the present invention, a plurality of organic EL elements having different emission spectrum distributions are vertically stacked on a substrate to emit light, for example, from emission dots. When the collected light is condensed on the surface of the recording medium W as an erect equal-magnification image, the SELFOC lens array can be used in a place where the MTF is optimal. In addition, since the SELFOC lens array can be used in common for the R, G, and B light emitting dots, it is more resistant to misalignment during assembly as compared with a conventional configuration requiring a SELFOC lens array for each color, Unevenness can be reduced.

Further, since the light emitting layers of the organic EL elements which emit light of each color are formed in substantially the same layer, the drive control of each light emitting dot becomes easy, the exposure delay is small, and the recording medium W High-quality exposure can be performed.

The light quantity of each light emitting dot is corrected so that the light quantity irradiated on the recording medium has an optimum color balance in accordance with the sensitivity characteristic of the recording medium. Exposure of a full-color image can be performed.

Since the power per unit area (drive current density) applied to the light emitting layer of each light emitting dot can be kept constant and the light amount can be corrected, the operating voltage can be shared and the light emitting layer of each light emitting layer can be used. The deterioration speed can be made uniform. As a result, the color balance does not change,
High-quality images with excellent color reproducibility can be stably obtained.

By arranging the light emitting dots so as to cover one line area in the main scanning direction of the recording medium by interpolating the gap in the main scanning direction, the influence of line defects in the main scanning direction is small, and A small number of images can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an organic EL printer including an organic EL print head according to the present invention.

FIG. 2 is a view showing an embodiment of an organic EL print head, and is a schematic plan view showing an outline of an electrode structure viewed from the outside of a substrate.

3 is a partially enlarged cross-sectional view of the organic EL print head, and is an enlarged cross-sectional view taken along line AA of FIG. 2 and observed from a main scanning direction.

FIG. 4 is a diagram showing an example of photosensitive material sensitivity characteristics of each color of red, green, and blue of a recording medium.

FIGS. 5A to 5D are diagrams showing examples of light emission patterns of light emitting layers.

FIG. 6 is a configuration diagram of an organic EL array print head disclosed in JP-A-9-226172.

FIG. 7 is a plan view of the head.

8 is a sectional view taken along line AA of FIG. 7;

[Explanation of symbols]

2 ... Organic EL print head, 3 ... Light emitting section, 21 ... Substrate, 22A, 22B ... Light emitting pattern group, 23 (23A-
23C) Organic EL element, 24 Anode (first electrode), 2
5 ... insulating layer, 26 ... organic layer, 27 (27A to 27C) ...
Light-emitting layer, 28: cathode (second electrode), W: recording medium.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yukihiko Shimizu 629 Oshiba, Mobara-shi, Chiba Futaba Electronics Co., Ltd. (72) Inventor Yoichi Kobori 629 Oshiba, Mobara-shi, Chiba Futaba Electronics Co., Ltd. Reference) 2C162 AE28 AE47 AF20 AF23 AF61 AH22 FA16 FA25 5C051 AA02 CA06 DA04 DA09 DA10 DB02 DB04 DB06 DB28 DB31 DC05 DC07 DE30 EA01 FA06

Claims (6)

[Claims] An organic layer including a light-emitting layer is formed on a substrate between a first electrode and a second electrode, at least one of which has a light-transmitting property. In an organic EL print head for forming an image by selectively irradiating light to a recording medium through an electrode having a light transmitting property, an organic layer including a light emitting layer between the first electrode and the second electrode Are stacked vertically on the substrate, and the emission dots of the plurality of organic EL elements are arranged in a row or in a staggered manner in the main scanning direction. An organic EL print head characterized in that: 2. The light emitting layer of each of the plurality of organic EL elements,
The light-emitting device is formed with substantially the same light-emitting area, and is driven to emit light by changing input power so that the amount of light applied to the recording medium matches the sensitivity of the recording medium and has an optimal color balance. Item 2. The organic EL print head according to Item 1. 3. The light-emitting layers of the plurality of organic EL elements are driven to emit light by inputting the same power, and the amount of light applied to the recording medium is adjusted so as to match the sensitivity of the recording medium and to achieve an optimal color balance. 2. The organic EL print head according to claim 1, wherein each of the light emitting layers is stacked from the substrate side in order from a light emitting layer having a low exposure ability, and the light emitting area is formed smaller as the light emitting layer has a higher exposure ability. . 4. The light emitting dots are arranged so as to cover an area of one line in the main scanning direction of the recording medium by interpolating a gap in the main scanning direction. The width and / or the width in the sub-scanning direction are changed so that the amount of light applied to the recording medium is adjusted to the sensitivity of the recording medium, and is formed with a light emitting area according to a luminance ratio that provides an optimal color balance. The organic EL print head according to claim 1. 5. The light-emitting dots have the same width between centers in the sub-scanning direction, and at least the width in the sub-scanning direction is changed so that the amount of light irradiated on the recording medium matches the sensitivity of the recording medium. 5. The organic EL print head according to claim 4, wherein the light emitting area is formed with a light emitting area corresponding to a luminance ratio that provides a good color balance. 6. The method according to claim 1, wherein the organic EL element is controlled so that the image of each color overlaps the same position on the recording medium in accordance with the image signal of each color, and a color image is formed on the recording medium by performing multiple exposure. The organic EL print head according to claim 1, wherein: